Fotogalerie chyba

<?php
//import
 require_once 'adresar.php';
//nastavení html 
 echo '<link type="text/css" href="hlavni.css" rel="stylesheet">
 <meta http-equiv="content-type" content="text/html; charset=utf-8"> 
        <link rel="stylesheet" href="css/lightbox.css" type="text/css" />
        <script src="js/jquery-1.7.2.min.js"></script>
        <script src="js/jquery-ui-1.8.18.custom.min.js"></script>
        <script src="js/jquery.smooth-scroll.min.js"></script>
        <script src="js/lightbox.js"></script>';
//práce se třídou Adresar  
 $class = new Adresar();
 $class->vyber();
 if (isset($_POST['ok'])) {
      echo '<h1> Aktuální složka: ', $_POST['vyber'], '</h1>';
   $class->vypis($_POST['vyber']);
 }
?>

<?php
    class Adresar{
    
    function __construct()
    { // BEGIN function __construct
     header('Content-type: text/html; charset=utf-8');
    } // END function __construct
    
    function vyber()
    { // BEGIN function vyber
    ?>     <h1>Potravinová Galerie</h1>
    <nav> 
        <form action="./index.php?action=fotogalerie" method="post">
       Vyberte jednu z následujících složek:<select name="vyber">
        <optgroup label="potraviny">
        <option value="potraviny/bio">/potraviny/bio</option>
        <option value="potraviny/dietni">/potraviny/dietni</option>
        <option value="potraviny/tucne">/potraviny/tucne</option> </optgroup>
        <optgroup label="tekutiny">
        <option value="tekutiny/alkoholicke">/tekutiny/alkoholicke</option>
        <option value="tekutiny/mlecne">/tekutiny/mlecne</option>
        <option value="tekutiny/neperlive">/tekutiny/neperlive</option>
        <option value="tekutiny/perlive">/tekutiny/perlive</option>  </optgroup>
         </select>
          <input type="submit" name="ok">
       </form> </nav>
        <?php 
    } // END function vyber
    function vypis($dir)
    { // BEGIN function vypis  
       $pole[1] = $dir;
         $slozka = dir($dir);
      $pocet = 0;
      ?>
      <div id="reference">
      <table>
      <tr>
      <?php
      while ($pole[2] = $slozka->read()) {
      if($pole[2] == "." || $pole[2] == ".."){continue;}
      $cesta = implode($pole, '/'); 
          echo'<td><a href="'.$cesta.'" rel="lightbox[reference]"><img src="'.$cesta.'" alt="'.$pole[1].'" title="'.$pole[1].'" width="150" height="150"></a></td>';
        ++$pocet;
        if($pocet == 4){
          echo'</tr><tr>';
         $pocet = 0;
        }   
      }       
      ?>
       </tr>
       </table> </div>
      <?php
      $slozka->close();
    } // END function vypis
    }
?>